 | | 9v Gear Motors
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| I have been searching lugnet for more info on the standard Lego 9v gearmotors. I know there are 4 terminals. I know there is forward, reverse, off (with braking) and float (without). Mark Overmar's NQC tutorial which is included with Dave Baum's (...) (24 years ago, 8-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| The motors are DC motors, with two terminals. A DC motor will reverse direction if the current direction is reversed. If the circuit to the motor coils are left open, no magnetic field is produced and the motor has no resistance to turn, so there is (...) (24 years ago, 8-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| There's nothing specially clever about the 9v geared motors. There are in fact only 2 terminals. The 4 connectors you see are just LEGO's clever way of supplying power to the motor regardless of the orientation of the power connector wire. So (...) (24 years ago, 8-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| Just went back and re-read the book, and in fact the RCX does do pulse width modulation and not voltage amplitude to set different power levels. In which case I'm not sure why effectively doing the same thing in NQC code works any better, but it (...) (24 years ago, 8-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| Conrad, if there are three states: on, off and float, there must be more than 2 terminals in use. Yes, there is PWM. According to the experts that changes the torque more than the speed. Under no load and a setting of (say) 2 you should see little (...) (24 years ago, 9-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| =>From: "Jerry Kalpin" <jdkalpin@sympatico.ca> =>... =>if there are three states: on, off and float, there must =>be more than 2 terminals in use. No, with two terminals (A & B), you can get: * A positive with respect to B => motor runs in one (...) (24 years ago, 9-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| Dave, A shorted to B (disconnected from the battery) might work if the motor acts like a generator when you turn it. But you try it. Even the smallest change in angle is resisted and with no spring-back. Un-motor-like. Jerry (...) (24 years ago, 9-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| Ah, that's why it changes the speed. The motors have a flywheel so pulses of on/float with no motor load will not appreciably change the motor speed. The inertia of the flywheel keeps the motor running during the float times. However, pulses of (...) (24 years ago, 9-Jun-00, to lugnet.robotics)
| | | | | Re: 9v Gear Motors
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| =>From: "Jerry Kalpin" <jdkalpin@sympatico.ca> =>... =>Dave, A shorted to B (disconnected from the battery) might work if the motor =>acts like a generator when you turn it. The motor *does* act like a generator when you turn it! Every once in a (...) (24 years ago, 9-Jun-00, to lugnet.robotics)
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